Upvote:2
Australian Citizens do NOT require a visa if they are visiting South Korea for the purposes of Tourism for stays up to 90 days. (Although as of about 10 years ago one IS required for business visits). The only documentation required will be proof of an onward journey out of South Korea (eg, a return plane ticket).
You can confirm this on the South Korean Consulate website for Australia - click on the link titled "Visa free for Australian passport holders"